serialize: don't panic on short buffer

Signed-off-by: Jay Lee <[email protected]>

protobuf-test/src/common/v2/test_basic.rs

@@ -5,6 +5,7 @@ use super::test_basic_pb::*;
 use protobuf::descriptor;
 use protobuf::reflect;
 use protobuf::CodedInputStream;
+use protobuf::CodedOutputStream;
 use protobuf::Message;
 use protobuf::ProtobufEnum;
 
@@ -302,3 +303,14 @@ fn test_parse_length_delimited_from_network_smoke() {
     assert_eq!(10, test1.get_a());
     is.check_eof().expect("check_eof");
 }
+
+/// Test if providing a smaller buffer, protobuf can detect and report error.
+#[test]
+fn test_serialize_too_large_message() {
+    let mut test1 = Test1::new();
+    test1.set_a(150);
+    let len = test1.compute_size();
+    let mut bytes = vec![0; len as usize - 1];
+    let mut s = CodedOutputStream::bytes(&mut bytes);
+    test1.write_to_with_cached_sizes(&mut s).unwrap_err();
+}

protobuf/src/coded_output_stream.rs

@@ -7,6 +7,7 @@ use crate::zigzag::encode_zig_zag_64;
 use crate::Message;
 use crate::ProtobufEnum;
 use crate::ProtobufEnumOrUnknown;
+use crate::ProtobufError;
 use crate::ProtobufResult;
 use crate::UnknownFields;
 use crate::UnknownValueRef;
@@ -134,7 +135,8 @@ impl<'a> CodedOutputStream<'a> {
                 self.position = 0;
             },
             OutputTarget::Bytes => {
-                panic!("refresh_buffer must not be called on CodedOutputStream created from slice");
+                return Err(ProtobufError::IoError(
+                    io::Error::new(io::ErrorKind::Other, "given slice is too small to serialize the message")));
             }
         }
         Ok(())